Protozoans, pond critters
What was the largest organism you observed
Spiral, rod, cocci
What three bacterial shapes did you observe
As you increase the magnification, the field of vision gets smaller
How does increased magnification affect the field of vision
So you don’t have to refocus the item you are looking at every time you increase the magnification
Why is it desirable that microscope objectives be parfocal
The highest magnification lens, in our case 100X or the oil immersion lens
Which objective focuses closest to the slide when it is in focus?
Iris Diaphram
Which controls on the microscope affect the amount of light reaching the ocular lens
There are 1,000 um in a mm. So there are 2,000 um in the field. Therefore: 1000 Bacillus would fit in the viewing field (2000um/2um). and 200 yeast (2000/10).
Assume the diameter of the field of vision in your microscope is two mm under low power. If one Bacillus cell is 2 u.m. how many Bacillus cells could fit end to end across the field? How many 10 u.m. yeast cells could fit across the field?
Brownian motion is the bombardment of cells by water molecules. The cells appear to be vibrating. True motility is movement of the cell by appendages. The cells move to and fro and the movement is more obvious
How did you distinguish true motility from Brownian movement or motion of the fluid?
Advantages of Hanging drop-Not flattened, so they behave more normally
-More details
-Can’t get out of the bubble, so they don’t leave field of view
-Stays moist
Disadvantages of wet mount-Kept having to focus in and out
-Things move in and out of view
-They dry out due to light
-Behaviors may change due to the spotlight.
-More details
-Can’t get out of the bubble, so they don’t leave field of view
-Stays moist
Disadvantages of wet mount-Kept having to focus in and out
-Things move in and out of view
-They dry out due to light
-Behaviors may change due to the spotlight.
What is the advantage of the hanging-drop procedure over the wet mount
they move around too quickly,they are not stained to give us the contrast of stained microbes,they are transparent thus blend with their habitat, they cannot be focussed on due to the motility
Why are microorganisms hard to see in wet preparations?
Yes, the cells of eukaryotic organisms have organelles bound by membranes (i.e. they’re compartmentalized) while much of the cellular machinery in prokaryotic cells is floating around freely.
Can you distinguish the prokaryotic organisms from the eukaryotic organisms?
Because the light is already being reflected in multiple places due to the drop of water. If oil was added to that, the light would be reflected even more, which would make the image worse.
WHy isn’t the oil immersion lens used in the hanging-drop procedure?
The lack of heat fixing or strong chemicals keeps from distorting the cell.
Why is the size more accurate in a negative stain than in a direct stain?
Darkfield technique
What microscopic technique gives a field similar in appearance to that seen in the negative stain?
Gram-Ethanol (alcohol)
Acid-Fast- Acid Alcohol
Acid-Fast- Acid Alcohol
What is the decolorizing agent in the Gram stain? Acid-fast stain?
TB and leprosy
What diseases are diagnosed using the acid-fast procedure?
Because they have a waxy coating around their cell, that prevents a lot of different things from getting into the cell. Including antibiotics if a person is sick. Making the chances of disease much more likely.
How might the acid-fast characteristic of Mycobacterium enhance the organism’s ability to cause disease?
mycobacterium are resistant to acid so the bacterium does not decolorize even when exposed to acid alcohol
In 1882, after experimenting with staining Mycobacterium, Paul Ehrlich wrote that only alkaline disinfectants would be effective against Mycobacterium. How did he reach this conclusion without testing the disinfectants?
Digestion removes unwanted bacteria, sputum, and human cells. It’s not used for staining others because it kills other bacteria
Clinical specimens suspected of containing Mycobacterium are digested with sodium hydroxide (NaOH) for 30 min prior to staining. Why is this technique used? Why isn’t this technique used for staining other bacteria?
Lipids, cryptosporidiosis or crypto
The acid-fast stain is used to detect Cryptosporidium protozoa in fecal samples. Which of the following would you expect to be a major component of their cell walls: carbohydrates, lipids, or proteins? What disease is caused by Cryptosporidium?
Rods and Spirals
Of what morphology are most bacteria possessing flagella?
Interfering with phagocytosis, capsule provides virulence to disease fighting cells.-can escape
phagocytosis
phagocytosis
How might a capsule contribute to pathogenicity?
Flagella make bacteria motile and allow them to spread on their own
How might flagella contribute to pathogenicity?
When conditions are unfavorable, the formation of an endospore allows the bacteria to remain in a dormant state until conditions become favorable.
Of what advantage to Clostridium is an endospore?
